I finally purchased a new Mac, a Mac Studio with M1 Max processor, and I am still in the process of setting up all the software and moving the data from the old one. The machine came with Monterey 12.4 preinstalled.
After a few troubleshooting issues and known Monerey issues I was able to solve, I noticed that when you use "Quick Look" from the desktop, the preview on my monitor (which is an old Cinema Display) is larger, uglier and the letters look a lot less crisp, and darker, than how they looked when I was using the old Mac Pro tower from 2010 running 10.11.6.
I see that the situation is not better in Font Book (I started using it, previously I handled fonts installment manually), but I can’t tell if this was the same under 10.11.6.
I find this annoying, as it was very handy to have a crisp and clear rendering to compare the letters on the fly after generating a new OTF version, with small drawing corrections.
I wonder if this is a choice on Apple part, affecting representation on the older Apple monitors, and thus unsolvable.
Has anyone running Monterey experienced something similar?
P.S. It also occasionally cuts the preview of Italic fonts: very ugly (see attachment).

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Comments
I noticed that Fontlab 7 rendering was also a bit worse, but not bad as the Desktop Quick Look rendering… Oh well, for now I’m stuck with the old Cinema Display.
I still don’t understand the cursor in the Quick Look window, though, and the ugly rendering without any margin. I guess this wouldn’t change with a brand new Retina monitor anyway.
defaults -currentHost write -g AppleFontSmoothing -int 0
as described on the website. I even have this option enabled for my retina display. You need to log out and back in for the setting to take effect.